I for one am actually nervous about the idea of trading in lower-level spells or powers for higher-level ones. Having to trade in low level powers in 4E was one of my bigger complaints about the system. It means that it is much more difficult to maintain continuity of a character's themes and specialties. What was once a signature move of your character gets replaced by completely unrelated new moves.
While the huge number of low-level spells wizards from 1-3e had were problematic, I'm not sure that eliminating lower-level slots once you reach higher levels will be a good idea. A complete overhaul of the spell slot system might have allowed for a better solution.
Right now, my biggest fear about 5E is that it might not be open enough to new ideas, and building upon the advancements and strengths of 3E and 4E. I'm afraid they might lean too close to rehashing old mechanics in order to please purists, and as a result alienate those who prefer newer style mechanics.